Ceramic Nanotechnology Lecture 4 Characterization of Nano and Micro Particles

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1 Universität Bremen

krezwan@uni-bremen.de Ceramic Nanotechnology – L4 www.bioceramics.uni-bremen.de

Ceramic Nanotechnology

Lecture 4

Characterization of

Nano and Micro Particles

Prof.Dr. Prof.Dr.--IngIng..

Kurosch Rezwan Kurosch Rezwan

krezwan@uni

krezwan@uni--bremen.debremen.de Bioceramics, FB4 Bioceramics, FB4 Universit

Universitäät Brement Bremen

Am Biologischen Garten 2, IW3 Am Biologischen Garten 2, IW3 D

D --28359 Bremen28359 Bremen Tel: +49 421 218 4507 Tel: +49 421 218 4507 Fax: +49 421 218 7404 Fax: +49 421 218 7404

http://www.bioceramics.uni

http://www.bioceramics.uni--bremen.debremen.de//

krezwan@uni-bremen.de

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Outline Course „

Outline Course

„Ceramic Nanotechnology

Ceramic Nanotechnology“

“

1. Introduction: Applications, Goals and Challenges 2. Powder Synthesis and Conditioning

3. Particle Interactions in Colloidal Systems 4. Characterization of Nano- and Micro Particles 5. Properties of Suspensions

6. Stabilization of Suspensions and Additives I 7. Stabilization of Suspensions and Additives II 8. Colloidal Processing and Rheology

9. Shaping Ceramics I: Bulk Materials 10. Shaping Ceramics II: Foams 11. Shaping Ceramics III: Thin Films

12. Sol – Gel Technology: From Molecules to Advanced Ceramics 13. Selected Applications of Ceramic Nanotechnology

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From Powder to Advanced Ceramics

Colloid Crystals Surface Micro Patterning

?

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Requirements for Ceramic Powder Synthesis

• Exact fixation of chemical composition

• Production of specific particle sizes and particle size distributions • High sintering activity

• Economic synthesis: broad application/usability of powders • Environment-friendly and energy saving processes

surface properties e.g. of colloid surface

Processing properties

crack formation/crack propagation

absence of large size secondary phases absence of agglomerates/aggregates

→low ppm range →defined microstructure composition

low impurity level in powder particles phase composition

→< 1 μm →narrow±10 % →uniform microstructure

homogeneity particle size

particle size distribution particle shape

Remarks Impact on finished part

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How to Characterize Nano and Micro Particles?

•Density

• Morphology

• Diameter & Size Distribution

• Specific Surface Area

• Surface & Bulk Composition

• Crystal Phase

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Outline Lecture

• Particle Morphology and Size

Density

Definition Particle Size Methods

• Other Particle Properties

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Overview Methods Particle Size Measurements

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Overview Methods Particle Size Measurements

Resolution

> 20 μm

1 nm - 5 μm

50 nm – 1000 μm

> 1 μm

1 nm – 100 μm

10 nm – 1000 μm

50 nm – 1000 μm

Method

Sieving

Light Scattering

Laser Diffraction

Coulter – Counter („Electrozone Sensing“)

Microscope (Optical / SEM / TEM)

Centrifuge Sedigraph with X-Ray Detection

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What is Porosity / Density?

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What is “

What is

“Particle Size

Particle Size”

”?

?

d_eq: equivalent diameter

2-dimensional:

circle with equivalent area as projection area of particle

3-dimensional:

sphere with similar total volume as particle

d

_eq

X_F: Feret diameter

Distance between 2 tangents to the particle contour

X_Fmin: smallest feret diameter

XFmax: largest feret diameter

X

_Fmin

X

_Fmax

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Cumulative and Differential Particle Size Distribution

cumulative volume distribution differential distribution

Particle Diameter D Particle Diameter D

d₅₀

The MEDIAN Diameter is called D50.

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Example Bimodal Distribution

D_Median≈30 µm

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Different Particle Size Definitions

volume distribution: the contribution to the mass is mostly caused by the bigger particles

numerical distribution (each particle

contributes)

Different Measurement methods can result in different results!

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Comparison number/volume distribution

volume distribution number distribution

Emphasis on small particles due to their large number.

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Light Microscope / SEM / TEM

Size Range > 1 µm > 10 nm SEM > 1 nm TEM

Advantage

Morphology directly observable No assumptions need to be made

Disadvantage SEM/TEM expensive Poor Statistics

Size Agglomerate: 5 µm Size Particle : 37 nm !

The National Bureau of Standards has stated that at least 10,000 separate images (not particles) need to be measured for statistical accuracy in image analysis

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Sieving

Size range > 20 µm

Advantage very cheap

Disadvantage

Not suitable for submicron and nano particles Low resolution

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krezwan@uni-bremen.de Ceramic Nanotechnology – L4 www.bioceramics.uni-bremen.de Scattering of light by particles.

Detector, shown in red, measures angles and light intensities.

The diffusion coefficient Dof the moving particles is obtained from the fluctuating scattering pattern. From the diffusion coefficient the hydrodynamic radius R_H is calculated.

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Particle Size: Light/Laser Scattering

1. The scattered lights from each particle reach to the to detector together

2. They interfere mutually.

3. As the particles move, the intensity of the scattered lights are changed with time.

Strenghtened Position

Scattered Light _Detec

tor Size Range

1 nm – 5 µm (Light Scattering) 50 nm - 5 µm (Laser Scattering) Advantage

Small particles measurable Disadvantage

Expensive, small particles may be concealed

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Coulter Counter (“

Coulter Counter (

“Electro sensing Zone

Electro sensing Zone”

”)

)

Particles suspended in a weak electrolyte solution are drawn through a small aperture, separating two electrodes between which an electric current flows. The voltage applied across the aperture creates a "sensing zone". As particles pass through the aperture (or "sensing zone"), they displace their own volume of electrolyte, momentarily increasing the impedance of the aperture. the pulse is directly proportional to the 3-dimensional volume of the particle that produced it.

Size range 1 - 100 µm

Advantage In situ usable

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Particle Size: X-

Particle Size: X

-Ray

Ray Sedigraphy

Sedigraphy

Particles falling in a liquid medium. Yellow line coming from the left represents the X-ray source. Not all the X-rays reach the detector. Amount of X-rays adsorbed by the sample represents the mass of particles at specific size.

Size Range 10 nm – 100 µm

Advantage

Wide size range, Particle Size and Distribution are measured

Disadvantage

Particles to be measured should not be X-ray transparent

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X-

X

-Ray Disc Centrifuge (XDC)

Ray Disc Centrifuge (XDC)

X – Ray Source

Detector Spinning

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X-

X

-Ray Disc Centrifuge (XDC)

Ray Disc Centrifuge (XDC)

(

)

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Acoustic Spectroscopy: Ultrasound

[Adapted from Meier L., Zürich]

Size Range 10 nm - 1000 µm

Advantage Fast technique that can be applied in situ without altering the system.

Disadvantage Only mono – and bimodal

characterization possible.

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BET Measurement: Specific Surface Area

From the amount of gas adsorbed on the surface the surface area is calculated.

Assumption: Monolayer Formation (Langmuir type of adsorption).

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BET Apparatus

Detection Range

> 0.2 m2_/g

Advantage

Best technique to determine the Specific Surface Area

Disadvantage

Particle Size Distribution not measurable

Particle BET

A

D

ρ

⋅

=

6

Calculation Particle Diameter: Gas Adsorption Method:

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BET Surface vs

BET Surface

vs

Particle Diameter for SiO

₂₂

1

Particle Size (μm)

0.01 0.1 1 10 100 1000

¾General Note: Repeatability/reproducibility of Particle Size MeGeneral Note: Repeatability/reproducibility of Particle Size Measurementsasurements

Relevance of Factors in repeatability and reproducibility

“Novices in the size-measurement field must understand that most errors in size measurement arise through poor sampling and dispersion and not through instrument inadequacies.”

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Outline Lecture

• Particle Morphology and Size

Density

Definition Particle Size Methods

• Other Particle Properties

Crystal Phase Zetapotential / IEP Elemental Composition Interfacial Tension

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Characterization of other Particle Properties

Output

Crystal Phase

Elemental Composition

Zetapotential / Isoelectric Point

Interfacial Tension

(Hydrophilicity / Hydrophobicity)

Method

X-Ray Diffraction (XRD)

X-Ray Fluorescence (XRF)

Colloidal Vibration Potential (CVP)

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X

-

Ray Diffraction (XRD): Determination of Crystal Phase

Outputs

Detection of crystal structure Crystallite size from peak broadening with Scherrer Equation

2 Θ

Counts/s

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¾XX--Ray Fluorescence (XRF): Determination of Elemental CompositionRay Fluorescence (XRF): Determination of Elemental Composition

Outputs

Detection of Single Elements and their Ratio

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Principle X

-

Ray Fluorescence (XRF)

1. An electron in the K shell is

ejected from the atom by an external primary excitation x-ray, creating a vacancy.

2. An electron from

the L or M shell “jumps in” to fill the vacancy. In the process, it emits a characteristic x-ray unique to this element and in turn, produces a vacancy in the L or M shell.

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The Colloidal Vibration Potential (CVP) Technique: Zetapotential

and IEP

Information about:

Zetapotential and Isoelectric point (IEP)

Accuracy: ±0.15 pH

±1 mV

Ø

ultra sound frequency ≈3 MHz

CVP

electrode

deflection particle

[Dukhin, Langmuir, 1999]

'

ϕ

C’: calibration constantϕ: volume fraction

μe: dynamic electrophoretic mobility

κ*: complex conductivity of dispersed system

ρp: density particle

ρm: density medium

Zg, Zs: acoustic impedances of

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Zeta Potential of selected Oxides and the IEP

-105

IEP towards basic pH

Definition Isoelectric Point (IEP): pH where the Zetapotential equals Zero.

Task

Determination of the interface and surface tension of liquids

Output

Measurement of the static interfacial or surface tension as a function of time or of temperature

Measurement of the adsorption/diffusion coefficients of surfactant molecules in oscillating/relaxing drops

Typical measuring range 0,05 ... 1000 mN/m and the resulting surface tension

γ

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krezwan@uni-bremen.de Ceramic Nanotechnology – L4 www.bioceramics.uni-bremen.de t0

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Interfacial tension measurement

1 2

where

γ

is the fitting parameter and the resulting surface tension

tequilibrium

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Surface Tension measured for Oxide Particle Suspensions

(at pH 7 in water/air,

Water, Silica

Alumina Titania

Zirconia

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Surface Tension measured for Oxide Particle Suspensions

Interpretation

Water Silica Titania Alumina Zirconia

S

ion [mN/m]

decrease surface decrease surface tension

tension

ÖSurface tension decreases in the following order

SiO2>TiO2>Al2O3>>ZrO2

hydrophobicity

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Outline Course „

Outline Course

„Ceramic Nanotechnology

Ceramic Nanotechnology“

“

1. Introduction: Applications, Goals and Challenges 2. Powder Synthesis and Conditioning

3. Particle Interactions in Colloidal Systems 4. Characterization of Nano- and Micro Particles 5. Properties of Suspensions

6. Stabilization of Suspensions and Additives I 7. Stabilization of Suspensions and Additives II 8. Colloidal Processing and Rheology

9. Shaping Ceramics I: Bulk Materials 10. Shaping Ceramics II: Foams 11. Shaping Ceramics III: Thin Films

12. Sol – Gel Technology: From Molecules to Advanced Ceramics 13. Selected Applications of Ceramic Nanotechnology